1. Field of the Invention
The present invention relates to a magnetoresistance effect film for reading the magnetic field intensity of a magnetic recording medium or the like as a signal and, in particular, to a magnetoresistance effect film which is capable of reading a small magnetic field change as a greater electrical resistance change signal, and further relates to a magnetoresistance effect type head using such a magnetoresistance effect film. These magnetoresistance effect film and magnetoresistance effect type head using such a magnetoresistance effect film are mainly incorporated in, for example, a hard disk drive.
2. Description of the Related Art
Recently, there has been the development for increasing the sensitivity of magnetic sensors and increasing the density in magnetic recording and, following this, magnetoresistance effect type magnetic sensors (hereinafter referred to as MR sensors) and magnetoresistance effect type magnetic heads (hereinafter referred to as MR heads) using magnetoresistance change have been actively developed. Both MR sensors and MR heads are designed to read out external magnetic field signals on the basis of the variation in resistance of a reading sensor portion formed of magnetic material. The MR sensors have an advantage that a high sensitivity can be obtained and the MR heads have an advantage that a high output can be obtained upon reading out signals magnetically recorded in high density because the reproduced output does not depend on the relative speed of the sensors or heads to the recording medium.
However, conventional MR sensors which are formed of magnetic materials such as Ni80Fe20 (Permalloy), NiCo or the like have a small resistance change ratio xcex94R/R which is about 1 to 3% at maximum, and thus these materials have insufficient sensitivity as the reading MR head materials for ultrahigh density recording of the order of several GBPSI (Giga Bits Per Square Inches) or more.
Attention has been recently paid to artificial lattices having the structure in which thin films of metal having a thickness of an atomic diameter order are periodically stacked, because their behavior is different from that of bulk metal. One of such artificial lattices is a magnetic multilayered film having ferromagnetic metal thin films and non-magnetic metal thin films alternately deposited on a substrate. Heretofore, magnetic multilayered films of an iron-chromium type, a cobalt-copper type and the like have been known. However, these artificial lattice magnetic multilayered films are not commercially applicable as they are because the external magnetic field at which a maximum resistance change occurs (operating magnetic field intensity), is as high as several tens of kilo-oersted.
Under these circumstances, a new structure which is called a spin valve has been proposed. In this structure, two NiFe layers are formed via a non-magnetic metal layer, and a pinning layer such as an antiferromagnetic layer is further formed so as to be adjacent to one of the NiFe layers.
In this case, since the antiferromagnetic layer and the NiFe layer adjacent thereto are directly exchange-coupled to each other, the direction of the magnetic spin of this NiFe layer is fixed in the range of several tens to several hundreds Oe in magnetic field intensity. On the other hand, the direction of the magnetic spin of the other NiFe layer is freely changeable by an external magnetic field. As a result, there can be achieved a magnetoresistance change ratio (MR ratio) of 2 to 5% in a small magnetic field range which corresponds to the degree of coercive force of the NiFe layer.
In the spin valve, by realizing a difference in relative angles of spins between two magnetic layers, the large MR change which differs from the conventional anisotropy magnetoresistance (AMR) effect is accomplished. This is realized by pinning of the magnetic layer spin due to the direct exchange coupling force between one of the magnetic layers and the pinning layer. This exchange coupling can be the substance of the spin valve.
The magnetic head using such a spin valve film can read out magnetic information recorded in ultrahigh density, however, following the high densification of hard disks, the demand for improving the spin valve type reading magnetic head ability has been increasing year by year. Further, it is demanded to develop a spin valve film structure, which is capable of reading magnetic information recorded in higher density and achieving higher outputs, and a magnetic head using such a spin valve film structure. In addition, it is also demanded that the linearity of a derived signal relative to an external magnetic field is excellent.
The present invention has been made under these circumstances and has an object to provide a magnetoresistance effect film which can achieve an increased head output and which is excellent in sensitivity for detecting a magnetic signal and in linearity of a derived signal, and further provide a magnetoresistance effect type head having such a magnetoresistance effect film.
For solving the foregoing problems, according to one aspect of the present invention, there is provided a spin valve type magnetoresistance effect film comprising a multilayered film including a non-magnetic metal layer, a ferromagnetic layer formed on one surface of the non-magnetic metal layer, a soft magnetic layer formed on the other surface of the non-magnetic metal layer, and a pinning layer which is formed on a surface of the ferromagnetic layer (remote from a surface thereof abutting the non-magnetic metal layer) so as to pin a direction of magnetization of the ferromagnetic layer, wherein the soft magnetic layer is set to freely change its magnetization direction in response to an external magnetic field as magnetic information, and wherein the soft magnetic layer comprises a multilayered body having at least two layers and including a first soft magnetic layer substantially made of Co or CoFe, and a second soft magnetic layer substantially made of NiFeX (wherein X represents at least one selected from Ta and Nb) in the order named from the side of the non-magnetic metal layer.
It is preferable that the second soft magnetic layer constituting part of the soft magnetic layer is substantially made of NiFeTa, and the percentage content of Ta is set to 1 wt % to 30 wt %.
It is preferable that the second soft magnetic layer constituting part of the soft magnetic layer is substantially made of NiFeNb, and the percentage content of Nb is set to 1 wt % to 15 wt %.
According to another aspect of the present invention, there is provided a spin valve type magnetoresistance effect film comprising a multilayered film including a non-magnetic metal layer, a ferromagnetic layer formed on one surface of the non-magnetic metal layer, a soft magnetic layer formed on the other surface of the non-magnetic metal layer, and a pinning layer which is formed on a surface of the ferromagnetic layer (remote from a surface thereof abutting the non-magnetic metal layer) so as to pin a direction of magnetization of the ferromagnetic layer, wherein the soft magnetic layer is set to freely change its magnetization direction in response to an external magnetic field as magnetic information, and wherein the soft magnetic layer comprises a multilayered body having at least three layers and including a first soft magnetic layer substantially made of Co or CoFe, a third soft magnetic layer substantially made of NiFe, and a second soft magnetic layer substantially made of NiFeX (wherein X represents at least one selected from Ta and Nb) in the order named from the side of the non-magnetic metal layer.
It is preferable that the second soft magnetic layer constituting part of the soft magnetic layer is substantially made of NiFeTa, and the percentage content of Ta is set to 1 wt % to 30 wt %.
It is preferable that the second soft magnetic layer constituting part of the soft magnetic layer is substantially made of NiFeNb, and the percentage content of Nb is set to 1 wt % to 15 wt %.
It is preferable that the thickness of the third soft magnetic layer, which constitutes part of the soft magnetic layer and is substantially made of NiFe, is set to 1 xc3x85 to 50 xc3x85.
According to another aspect of the present invention, there is provided a magnetoresistance effect type head comprising a magnetoresistance effect film and a conductive film, the conductive film being conductively connected to the magnetoresistance effect film, and the magnetoresistance effect film being a spin valve multilayered film including a non-magnetic metal layer, a ferromagnetic layer formed on one surface of the non-magnetic metal layer, a soft magnetic layer formed on the other surface of the non-magnetic metal layer, and a pinning layer which is formed on a surface of the ferromagnetic layer (remote from a surface thereof abutting the non-magnetic metal layer) so as to pin a direction of magnetization of the ferromagnetic layer, wherein the soft magnetic layer is set to freely change its magnetization direction in response to an external magnetic field as magnetic information, and wherein the soft magnetic layer comprises a multilayered body having at least two layers and including a first soft magnetic layer substantially made of Co or CoFe, and a second soft magnetic layer substantially made of NiFeX (wherein X represents at least one selected from Ta and Nb) in the order named from the side of the non-magnetic metal layer.
According to another aspect of the present invention, there is provided a magnetoresistance effect type head comprising a magnetoresistance effect film and a conductive film, the conductive film being conductively connected to the magnetoresistance effect film, and the magnetoresistance effect film being a spin valve multilayered film including a non-magnetic metal layer, a ferromagnetic layer formed on one surface of the non-magnetic metal layer, a soft magnetic layer formed on the other surface of the non-magnetic metal layer, and a pinning layer which is formed on a surface of the ferromagnetic layer (remote from a surface thereof abutting the non-magnetic metal layer) so as to pin a direction of magnetization of the ferromagnetic layer, wherein the soft magnetic layer is set to freely change its magnetization direction in response to an external magnetic field as magnetic information, and wherein the soft magnetic layer comprises a multilayered body having at least three layers and including a first soft magnetic layer substantially made of Co or CoFe, a third soft magnetic layer substantially made of NiFe, and a second soft magnetic layer substantially made of NiFeX (wherein X represents at least one selected from Ta and Nb) in the order named from the side of the non-magnetic metal layer.
In the present invention, since the soft magnetic layer, which is set to freely change its magnetization direction in response to an external magnetic field as magnetic information, is composed of the predetermined materials in a laminate fashion, there can be obtained a magnetoresistance effect film which is excellent in detecting sensitivity and which can achieve an increased head output.